This invention relates generally to the cooling system of vehicle engines and, more particularly, to the radiator receiving water heated in the engine block of the vehicle which is then cooled in the radiator by air flowing through the latter either by virtue of the forward movement of the vehicle or a fan urging this air through the radiator.
Conventionally, a radiator has been provided with a filler tube to which is fitted a filler cap having a pressure-relief valve which is disposed to open when the nominal operating pressure of the engine cooling system, of which the radiator forms part, is exceeded. For many years, any coolant flowing through the pressure-relief filler cap valve was merely drained to ground, whereby the overflow coolant was lost. Accordingly, it was necessary regularly to check the coolant level and effect a top up as and when necessary.
In more recent years, the engine cooling systems have been modified in order to conserve any overflow coolant. In one arrangement, a separate coolant recovery or overflow bottle has been provided which is connected to the radiator by a hose and is vented to atmosphere. Any coolant discharged from the radiator due to an excessive increase in coolant pressure in the cooling system, overflows from the radiator into the recovery bottle and is then syphoned back into the radiator when the coolant therein cools. This arrangement works very satisfactorily inasmuch as it eliminates, as far as possible, the introduction of air into the coolant when the overflow coolant is syphoned back into the radiator. This is important because any aeration of the coolant is likely to cause air pockets which, if located within the engine block, can cause undesirable hot spots and furthermore, aeration also can give rise to cavitation which can have an erosive effect. However, the disadvantage of the recovery bottle system is that it increases the component count of the engine cooling system and entails extra assembly operations, and hence, increases manufacturing costs.
An alternative arrangement is to provide a de-aeration tank at the top of the radiator which tank, unlike the recovery bottle, is subjected to the pressure of the cooling system and it is found that the exclusion of air from the coolant subsequently being returned to the radiator from the de-aeration tank is not as efficient as it might be. Accordingly, the deleterious effects of air in the coolant discussed above can manifest themselves with such an arrangement.
It has been found to be desirable to resolve the problems of the aforementioned known vehicle cooling systems by providing a system based on the simple, but highly effective, concept of combining these two prior solutions to the problem of conserving overflow coolant so as to obtain the advantages of lower component count and more efficient de-aeration of the coolant.